I found this thread useful so am replying to it ..even though it is slightly old.
IDD, International calls to UK, cheap phone calls to UK.
http://www.ectelecom.com/eng/promotion.htm
This company is doing 24x7 promotional rate calls to these destinations (fixed lines) China, USA , Canada, Australia, UK, France, Germany, Italy,
Japan, Malaysia, Netherlands, New Zealand, Singapore, South Korea, Taiwan, Sweden, Switzerland
for 9 cents per minute until 2 July 2006
You can register several lines (mobile and land line) and just dial an access number.
All you need is an address, id card ..they allow several payment methods.
Meerkat